We propose to study the biochemical alterations in the plasma membrane which may be important in transmitting the signal for lymphocyte activation from the exterior to the interior of the cells, with major emphasis on the role of cyclic nucleotides. Protein phosphorylation will be examined in lymphocytes prelabeled with 32PO4 and incubated with mitogenic agents, nonmitogenic lectins, and agents which augment or inhibit the activation process, as well as cyclic nucleotides, utilizing sophisticated fractionation techniques to separate phosphorylated proteins. In addition, plasma membranes will be isolated from resting human peripheral blood lymphocytes, activated lymphocytes and two human lymphoblast cell lines and examined for alteration in adenylate and guanylate cyclase, cyclic nucleotide binding and cyclic nucleotide dependent and independent protein kinase activity of endogenous and exogenous substrates in the presence of gamma 32P ATP of high specific activity. Kinase activity will be examined in the presence and absence of regulatory and catalytic subunits of rabbit skeletal muscle protein kinase and kinase inhibitor protein. An attempt will be made to solubilize and characterize plasma membrane associated protein kinases and determine if they are the same or distinct from soluble kinases present in the cytosol. Proteins phosphorylated during the activation process will be isolated and compared in terms of their physicochemical and immunochemical properties with plasma membrane proteins phosphorylated in a cAMP dependent manner in other cell systems. Finally we will examine the effects of other agents which modulate the activation process: sulfhydryl reagents, cytochalasins, colchicine and vinblastine, periodate, trypsin, heavy metal ions, divalent cations (particularly calcium), phospholipids, and fatty acid on cyclic nucleotides and protein kinases, as well as on noncyclic nucleotide related biochemical events which occur during the activation process. It is our expectation that these studies will provide additional insight into the activation processes, provide new approaches to the study of immunologic deficiency states and eventually to new changes and approaches to the manipulation of the immune response.